In metal-air batteries, oxygen contained in the atmosphere is used as a cathode active material so that an oxidation-reduction reaction with the oxygen takes place at an air electrode as a cathode. On the other hand, an oxidation-reduction reaction with a metal takes place at a metal electrode as an anode. Metal-air batteries have high energy density and have expectations for serving as emergency power supplies, etc., at the time of a disaster, or the like. Such metal-air batteries that have expectations for serving as emergency power supplies, or the like, are generally configured of a plurality of metal-air battery cells in accordance with a desired electrical output and start generating power upon an electrolytic solution being filled into each metal-air battery cell.
A desired output can be gained by connecting and unitizing a plurality of metal-air battery cells. The structure of a battery unit is disclosed in each of the following patent literatures Japanese Unexamined Patent Publication No. 2013-214472, Japanese Unexamined Patent Publication No. 2013-214473, and Japanese Unexamined Patent Publication No. S62-177873.